AbstractThe burrowing squamates of the order Amphisbaenia lack external ears. The middle ear involves an extremely large stapes with the head of its shaft (columellar portion) projecting just posterior to and as far laterally as the quadrate. In most species a cartilaginous extracolumella articulates with the distal tip of the shaft and then stretches along the lower jaw and is attached to the skin in the region of the second infralabial. Records of the electrical potentials of the cochlea in some nine species show sensitivity curves whose maxima are approximately −20dB for a standard output of 0.1 μv. The zone of greatest sensitivity lies in the low frequencies, usually between 300 and 700 Hz. The sensitivity of amphisbaenians differs from that of snakes in being fairly good above levels of 700 Hz, where the latter drops off sharply. Interruption of the extracolumella causes a 20 to 30 dB loss in sensitivity. Sound waves applied asymmetrically produce different electrical responses in the two ears, suggesting an explanation for behavioral observations on the utilization of the syst